In commenting on this thread http://boards.straightdope.com/sdmb/showthread.php?threadid=111012 , I referred to what I called “Oirish”. I said it is an occult dialect found only in American and British films. It bears little relation to any dialect or accent actually existing in Ireland.
This “Irish” dialect or accent has grown its own vocabulary. In particular, it has developed a word “begorrah”, which is routinely used when imitating Irish people.
In nearly fifty years in Ireland, I have never heard an Irish person use “Begorrah” in normal conversation. They only use it to poke fun at stage Irish or Oirish images of Ireland. They use many parallel abbreviations or distortions of “by god”, but not that particular formation.
Where did this word come from, and why is it seen as the typical Irish exclamation?